<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
</head>
<body>
<script>
    //chartAt（）返回值是字符串。
    var arr = 'abcdefg';
    console.log(arr.length);//7
    console.log(arr.charAt(1));//b//注意此处的返回值
    console.log(arr[1]);//b

</script>
</body>
</html>